In order to accommodate torque transfer and potentially misalignment between rotatable members such as shafts, flexible couplings have been employed. Such couplings are connected by flanges or spline connections and are specifically designed to transmit torque from one component to the other component while absorbing and dissipating the effects of misalignment.
While many such couplings exist, all suffer from limited degree of flexibility. One common way of increasing misalignment tolerance is to incorporate additional flexible elements. This however results in a heavier and more expensive construction as well as commonly the introduction of additional stress risers occasioned by the manufacturing process. Some increased flexibility can be obtained but with diminishing returns.
A common causative factor related to prior art couplings failing is the development of fatigue fractures. These can develop both from a lack of flexibility (rigidity) overall in the coupling and from individual stress risers within the coupling. Some of the structural rigidity (material and stress risers) of currently available commercial designs comes from the means of manufacture of the coupling. One example of a process commonly associated with stress risers being introduced to a coupling is a welding process to join adjacent diaphragms. Welding causes localized phase change in the metal of the disks often resulting in a change in hardness and heat-treating properties of the coupling in the local region. Another weakness of prior art couplings is that they can have very low axial stiffness due to inherent design factors and method of construction. This low stiffness can lead to vibration problems that can produce failures of flexing elements.
The foregoing and other drawbacks inherent in the prior art have been tolerated for an extended period of time because there was no viable alternative. This fact notwithstanding, the art would be very much benefited by the availability of a more durable flexible coupling.